The present invention relates to an apparatus and process for the removal of undesired particulates and microorganisms from water and other liquids. More particularly, the present invention relates to an apparatus and process for the more efficient filtration of liquids such as water.
Water intended for human consumption is expected to be either free of harmful constituents or contain concentrations of such constituents that are below harmful levels. To provide potable water for use in homes and businesses, municipalities utilize industrial scale processes in an effort to eliminate or reduce harmful constituents present in water drawn from large, naturally occurring water sources. Potable water is also frequently obtained on a smaller scale from wells and springs and usually without any treatment prior to consumption.
Unfortunately, the potability of a particular water supply is sometimes questionable. The consistency and efficiency of treatment by municipalities may vary due to numerous factors such as heavy rainfall, equipment failures, and usage levels. Depending upon the seriousness of a variation in treatment, a municipality may be forced to notify its consumers that further treatment of the water supplied, e.g. boiling, is required at the point of use before consumption is safe. Water obtained directly from a natural source may also become suspect depending upon environmental conditions near the source. For examples, wells and springs can be contaminated due to rain water run-off washing a contaminant into the source. Accordingly, a need exists for liquid filtration devices suitable in size and scale for residential or office use.
In response, liquid filtration devices have been developed. Such devices range from those located at the point-of-use (e.g. the spigot of a kitchen sink, gravity-flow dispensers such as water pitchers, and low-pressure dispensers such as sports bottles) to the generally bulkier point-of-entry units hidden from view within the plumbing of a home or office. Many of these devices use activated charcoal in at least one stage of the filtration process. Activated charcoal helps to remove strong odors and tastes from water. More specifically, activated charcoal can remove chlorine, and sediment from water.
A problem associated with the use of activated charcoal (also referred to as activated carbon) is that certain microorganisms, like bacteria, propagate rapidly within activated charcoal. This problem has at least three undesirable effects. First, the growth of bacteria within the charcoal may inhibit the flow of water through this stage of the filter. Second, and more importantly, the use of activated charcoal can actually increase the concentration of bacteria present in the water by providing a moist, nutrient-rich environment that is conducive to bacterial reproduction as described in Daschner et al., Microbiological Contamination of Drinking Water in a Commercial Household Water Filter System, 15 Eur. J. Clin. Microbiol. Infect. Dis. 233xe2x80x9437 (1996). Third, for those uses that are intermittent, the first flow of water through the activated charcoal after a period of nonuse will contain a spike concentration of bacteria.
Typically, a certain concentration of bacteria is present in all water supplies. This concentration can increase in activated charcoal that is not flushed by the periodic use of water from a particular filter. The result is a spike concentration present in each intermittent use as the bacteria is flushed form the activated charcoal. Increased bacteria concentration is the opposite result intended by the filter installation. While many filtrations mechanisms are available, none address all of these challenging problems without frequent replacement of the activated charcoal.
U.S. Pat. No. 5,271,837 describes a multistage system for the filtration of drinking water utilizing a central filter cartridge constructed of activated charcoal impregnated with silver, a cation exchange resin, and an anion exchange resin. The activated charcoal is the first stage of the filtration system, followed by the resins. To prevent particulates from clogging the central filter cartridge, U.S. Pat. No. 5,271,837 discloses a particulate filter located prior to the central filter cartridge. This patent, however, does not address any problems unique to the filtration of microorganisms or the prevention of bacteria growth on the activated charcoal.
U.S. Pat. No. 5,891,333 describes a modular, multistage water filter for use in countertop or below-countertop applications. This patent is directed to a device with removable, replaceable cartridges containing filter media within a configuration that permits changes in size scale depending upon the filtration capacity desired. The disclosure does not specify any particular filter media or constituent filtration sequence. The removal of any particular constituent from a water supply is not taught.
U.S. Pat. No. 5,318,703 describes a water filter module for use in coffee brewing that is designed to remove residual chlorine, odors, foul tastes, impurities, and unspecified other sediments from water prior to contact with the coffee grinds. The filter media disclosed is activated carbon which is held in place by mesh screens. The mesh screens, which may be a polymer material, are included to remove large particulate impurities, such as sediment and other dirt particles, by mechanical filtration. The removal of microorganisms or any specific problems associated therewith is not addressed.
A disposable filter constructed of a paper filter media is presented in U.S. Pat. No. 5,554,288. Finely-divided adsorbents are uniformly distributed throughout a pulp from which a paper filter media is created for use in variety of configurations. Various adsorbents are claimed, including activated carbon. U.S. Pat. No. 5,554,288 specifically recognizes that carbon filter cartridges that remain immersed in the water being treated may become a hospitable medium for bacteria growth. However, as claimed, this particular problem is avoided because the filters of U.S. Pat. No. 5,554,288 are discarded after use rather than remaining immersed in the water. This solution, however, requires the user to frequently replace the filter, and requires disposal of the spent filter.
Therefore, a need has existed for an improved method and apparatus for the removal of undesired particulates and microorganisms, such as bacteria, viruses, protozoans, yeast, fungi, and microbiological cysts, from liquids such as water. More particularly, a need for an improved method and apparatus for the filtration of liquids with greater filtration efficiency and the elimination of spike concentrations of microorganisms has existed that is not addressed by the prior art.
The present invention addresses some of the problems identified above by providing a method and apparatus for filtering fluids such as water that reduces bacteria contact with the activated charcoal stage of the filter. More specifically, a filter stage is placed in the water stream of a multistage filter at a point in flow prior to the activated carbon such that the microorganisms are substantially removed from the water prior to the filtration by the activated carbon.
By consequently preventing bacteria contact with the activated charcoal, the problems of increased bacteria concentration and associated flow reduction are avoided. For uses that are intermittent, the problem of spike concentrations is avoided by preventing the in microorganisms from reaching the activated carbon where conditions for reproduction may be conducive during periods of no water flow.
Multiple embodiments of the invention may be employed. For example, the filter may consist of stages in the form of beds of material in a stacked configuration within a cylindrically- or otherwise-shaped chamber. The liquid may enter the chamber from one end, pass longitudinally through the various stages of filter media, and then exit the chamber to a point of use. Other configurations of the filter system are also within the scope of the present invention and modifications to the structural configurations should not affect the ability of the presently-inventive apparatus and process to effectively filter fluids such as water. It should be understood that while a water filtering process is exemplified herein, the present process and apparatus may be utilized for filtering other liquids depending on the contaminant removal characteristics desired.
The beds of material utilized in the present invention may include beads, resins, granular materials, or compressed adsorbents and may be charged or uncharged. Alternatively, in another embodiment, the filter may consist of stages in the form of sheets or webs of filtration media layered together through which the water is caused to flow. Each sheet may be constructed of a filtration media specifically designed for the removal of certain constituents. In still another embodiment, the filter may consist of stages in the form of concentric, cylindrical layers where water is caused to flow either radially inward or outward through the layers and then on to the point of use.
The scope of the present invention is not limited to any particular embodiment set forth herein. Instead, the present invention requires that, regardless of a particular embodiment, configuration, or shape of the device in which the filter is housed or used, the liquid is filtered prior to flow through the activated carbon using a filter media that removes microorganisms. As used herein with respect to action relative to microorganisms, xe2x80x9cremoval of microorganismsxe2x80x9d includes the killing, capturing, or deactivation of such microorganisms.
In addition, without limiting the scope of the present invention, additional stages of filter media may be added to the filter, depending upon the constituents sought to be removed. These stages may be located before or after the stage which includes activated charcoal. Again, the present invention requires that at least one stage for the removal of microorganisms precedes the stage containing activated charcoal.
The entire filter apparatus, having at least two stages, may be assembled into a variety of physical shapes and configurations depending upon the intended consumer or application. For example, and without limiting the scope of the present invention, a device containing the filter media may be readily attached to the spigot of a kitchen sink or other tap supplying water. In still another configuration, a device containing the filter unit that fits into a cabinet or within the plumbing of a residence or business may be utilized. Other embodiments include the use of the apparatus in a pitcher, sports bottle, or other dispenser.
In one particular embodiment of the present invention, water entering the filter apparatus first passes through a stage constructed of a meltblown web, a charge-modified meltblown, a glass fiber web, or a charge-modified glass fiber web. This stage acts to remove turbidity-related components which may act to cloud the liquid and various sediments, as well as certain organic components. The water then passes through another stage constructed of a one or more microporous materials such as microfiber glass. Microorganisms, including bacteria, are primarily removed by this stage.
Subsequent to these two stages, the water passes through a stage of activated carbon where other impurities are removed through adsorption. As the bacteria has already been removed prior to this stage, the activated carbon becomes less fouled with microorganisms such as bacteria.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the principles of the invention.